CLI: Introduce --nohz_full/-N entity

This will set as the cpu list what was configured on the nohz_full=
kernel command line argument, allowing isolating these CPUs and then
moving to it some important app, i.e. all the other operations one
can do in tuna can apply to that cpu list.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>